In my 2 1/2 cents opinion on the tail motor, normally a brushless main motor is designed for 11.1v atleast. Therefore, to suit this mod, you have to use an 11.1v tail motor as well, be it a brush or be it a brushless tail motor.

A guy named hadriez sent a video (on youtube) of him flying an f45 using a brush tail set of a walkera v400d02 if im not mistaken. I have posted the video here previously. I think this tail set is suitable to compensate an 11.1v system (as the tail motor is designed for 11.1v also) and the boom is longer than the stock too which may help to introduce a more stable flight.

I had posted that video already in this thread quite a long time ago and we had already talked about the possibility to change the length of the tail boom, and use an 11.1volts battery like Hadriez is using seemingly with no trouble at all!! IMO the BL setup main motor works quite well with 7.4 volts only thing is you have to limit your flights to about 9 mins because after the 10min mark you start losing power and tail authority is highly affected when battery is low!! Also I think that if you increase the length of the tail boom you will increase that strange bobbing that sometimes seems to afflict the F45 in certain situations!! Basted wind is blowing hard again today and I overslept this morning so didn't get the chance to test the walkera blades yet outside

I had posted that video already in this thread quite a long time ago and we had already talked about the possibility to change the length of the tail boom, and use an 11.1volts battery like Hadriez is using seemingly with no trouble at all!! IMO the BL setup main motor works quite well with 7.4 volts only thing is you have to limit your flights to about 9 mins because after the 10min mark you start losing power and tail authority is highly affected when battery is low!! Also I think that if you increase the length of the tail boom you will increase that strange bobbing that sometimes seems to afflict the F45 in certain situations!! Basted wind is blowing hard again today and I overslept this morning so didn't get the chance to test the walkera blades yet outside

Thanks for the credit Mate... Well, what do you know! my 2 1/2 cents thought turned out to be not bad at all!...... and just for your info, not necessarily caused by a longer tail boom, bobbing or jerking usually associated with a weak / malfunction or overheated tail motor.. If you often encountered this problem, try to use heat sink just to prolong the life span of the tail motor..

I think the main drawback of a longer tail is that during forward flight, it acts more strongly like a wind vane, and will take more effort to make it turn.

A shorter tail will improve responsiveness since it has less front-to-back resistance. Also a longer tail mean larger turning circle for the tail, so while the tail will have more "leverage". Even stationary pirouettes will be slower as it has to travel further to complete a rotation.

I think the main drawback of a longer tail is that during forward flight, it acts more strongly like a wind vane, and will take more effort to make it turn.

A shorter tail will improve responsiveness since it has less front-to-back resistance. Also a longer tail mean larger turning circle for the tail, so while the tail will have more "leverage". Even stationary pirouettes will be slower as it has to travel further to complete a rotation.

Food for thought

This is an awesome explanation and really make sense... thanks & cheers...

Thanks for the credit Mate... Well, what do you know! my 2 1/2 cents thought turned out to be not bad at all!...... and just for your info, not necessarily caused by a longer tail boom, bobbing or jerking usually associated with a weak / malfunction or overheated tail motor.. If you often encountered this problem, try to use heat sink just to prolong the life span of the tail motor..

I don;t worry about the life span of my tail motor it has been going strong since april 2012 so far

You will definitely need a pinion to fit on the BLmotor shaft as stock won't fit since it's 2mm shaft!! I don't know if this combination will work but on someone on youtube had success with a BL inrunner motor on his F45 I will try to search the link for you.

ESC is fine, anything more than 12 Amps should work I believe. Higher amps means less chance of it overheating under heavy load. eg if the motor pulls 10A at full stress, the 12A ESC will get quite warm, where as the 18A wont get very warm at all.

In terms of the Motor, the one you linked will work, however, you will need to modify the body of the F45 either by cutting or bending, or both, as it only has a 24mm space where the motor sits, and that motor you chose is 26mm wide.

Some time ago word was going around that a heat sink won't be able to lower the heat significantly.
Today I measured the temperature of two more flights, giving a total amount of 6 times flying with heatsinks installed head and tail.
It does help a lot! Not only during the flight, but the cool-off effect after landing is also much faster...
I didnt look at the temperature at each flight. But the head + tail motor are still running smooth after a total of 48 flights.

more interesting are the temperatures measured at the main motor because i didnt measure the tail motor's heat until i installed the heatsink.
the temperatures of the first few flights were lower because i was very carefull not to destroy the mjx instantly.
The first higher peaks indicate when i was able to fly harder.

ESC is fine, anything more than 12 Amps should work I believe. Higher amps means less chance of it overheating under heavy load. eg if the motor pulls 10A at full stress, the 12A ESC will get quite warm, where as the 18A wont get very warm at all.

In terms of the Motor, the one you linked will work, however, you will need to modify the body of the F45 either by cutting or bending, or both, as it only has a 24mm space where the motor sits, and that motor you chose is 26mm wide.

I think I'm going to order the EH-200 from another vendor depending on their shipping costs. I'm trying to decide if I should try the 5000kv version with stock voltage like in the video or go for the 4100kv version and get a new 3C Lipo. I think I can convert for ~ $50-$75. My hope is that will tie me over until I pick up one of those Carbon Fibre frames and start building one of those up, or go for the same in a Quad.

Some time ago word was going around that a heat sink won't be able to lower the heat significantly.
Today I measured the temperature of two more flights, giving a total amount of 6 times flying with heatsinks installed head and tail.
It does help a lot! Not only during the flight, but the cool-off effect after landing is also much faster...
I didnt look at the temperature at each flight. But the head + tail motor are still running smooth after a total of 48 flights.

Hell Störsender, the word was from me !
Of course the heatsink helps to lower the temp, but essentially at the outside of the motor (housing and magnets of the stator)
But what gets the hotest are the rotor and the brushess, wich are not in contact with the heatsink, and are therefore just marginally cooled by the heatsink.
On my first F45, both motors have heatsinks, tail motor died after 50 flights, and main motor after 55 flights.

I think I'm going to order the EH-200 from another vendor depending on their shipping costs. I'm trying to decide if I should try the 5000kv version with stock voltage like in the video or go for the 4100kv version and get a new 3C Lipo. I think I can convert for ~ $50-$75. My hope is that will tie me over until I pick up one of those Carbon Fibre frames and start building one of those up, or go for the same in a Quad.

I would not suggest the 5000kv on 7.4 volts.
I used that in my firefox CP and it did not work well. With full battery, it was OK.
When battery got to about 7.8 to 7.9 volts, the power was hardly enough to keep in the air and that heli is half the weight of the F45.